This invention concerns a method and the relative apparatus used, in the field of medical analyses, to determine the speed of sedimentation of blood (xe2x80x9cESRxe2x80x9d), and also other parameters correlated thereto, such as viscosity, elasticity, density or otherwise.
In the field of medical analyses, to ascertain pathological states defined as inflammatory, the speed of sedimentation of the corpuscular part of the blood is measured, particularly the erythrocytes or red cells.
To establish the ESR, various methods have been adapted but these have not proved to be completely satisfactory, in that detection is neither quick nor practical.
In these methods, which use different measuring systems, the blood taken from the patients is put into tubular containers and subsequently, possibly after centrifuging, the due measurements are made on the blood samples.
Other systems provide to detect, at pre-set intervals of time, the position of the separation interface between the fluid plasma part of the blood, substantially clear, and the corpuscular part consisting of red and white cells and platelets, which is more turbid.
Other systems provide to detect the optical density or absorbance of the blood in correspondence with the separation interface.
Other cases provide to use optothermic sensors suitable to detect at defined intervals the heat produced by the blood sample absorbing radiation which strikes it.
The different methods to determine ESR which have been proposed until now are all characterized by an initial dead time which has a considerable influence on the time required for analysis; the latter cannot therefore be done in succession with other analyses which are much quicker, such as for example blood cell counts.
Conventional methods, moreover, have to use disposable containers, which entails an increase in costs both to purchase them and to dispose of them. Furthermore, the quantity of blood needed to do the analysis is high, and this entails problems in some particular cases, for example when the analysis involves children.
The state of the art also includes a method, proposed by the same Applicant, which provides to withdraw the blood to be analyzed from the container in which it is kept and to introduce the blood into a measuring volume, of limited thickness, which is used for various measurements made on different samples.
This method is based on the detection of the optical density or absorbance of the blood at a fixed point of the measuring volume, which is made to rotate to accelerate the sedimentation of the blood.
The means used to detect the absorbance comprise devices to emit/detect electromagnetic radiations associated with the measuring volume. The absorbance values detected are directly proportional to the number of cells in the blood sample at the point of observation, and this number varies over time due to the effect of the sedimentation of the cells.
By studying the absorbance over time it is possible to obtain the ESR value by eliminating the initial dead times and obviating the need to use disposable containers for the analysis.
Moreover, the quantity of blood needed is less and therefore the analysis can be done without any problems, even on paediatric patients.
Although it has these advantages, the method is also characterized by some problems which prevent it from being used in a completely satisfactory manner.
The size of the apparatus used to measure the ESR and the difficulties involved in managing several centrifugal means limit the possibility of using the system with an integrated instrument for counting the blood cells. Moreover, the size of the apparatus requires the analyses to be made in the laboratory and the method of analysis itself still requires volumes of blood which are in any case considerable.
Furthermore, after every measurement, the centrifugal means and the volume associated therewith always have to be repositioned with respect to the emission/detection means, which creates problems and anomalies in controlling the flow of blood.
In this apparatus, after each test, the blood sample is discharged and a new blood sample is introduced into the measuring volume.
To avoid washing the measuring volume after discharge, the residue of the sample which has already been analyzed is discharged by the new blood sample to be analyzed, since the hydraulic path which the blood has to follow to avoid pollution is rather long; this increases the volume of blood which has to be used.
A further limit of this method is that the acquisition of the photometric data depends on the speed of rotation of the measuring volume and therefore cannot be considered a continuous phenomenon.
The Applicant has devised and embodied this invention to perfect and extend the field of use of the apparatus described above, and also to obtain further advantages.
The invention is set forth and characterized in the respective main claims, while the dependent claims describe other characteristics of the invention.
The purpose of the invention is to supply a method and the relative apparatus to determine the speed of sedimentation of blood, and other parameters correlated thereto, which will allow a rapid, easy and reliable analysis which can be done in combination with haematological analyses of a different type.
Another essential purpose of the invention is to allow the apparatus to be integrated into existing systems for blood cells counting, thus exploiting the homogenisation of the blood already achieved by said systems.
Another purpose is to achieve a compact apparatus which is easy to transport, practical to use under any conditions and in any environment and which can also be used as an instrument in the ambulatory or hospital.
A further purpose of the invention is to eliminate the need to centrifuge the container and hence all the problems relating to its integration with other devices, controlling the flow, discontinuity of monitoring, etc.
The apparatus to determine ESR according to the invention comprises a capillary container, transparent to the electro-magnetic radiations within a certain field of wavelengths, with at least a substantially rectilinear segment and of extremely limited size inside which the blood to be analyzed is introduced.
The apparatus also comprises pump means suitable to send a blood sample inside the capillary, so that the blood sample can be passed through by an electromagnetic radiation emitted by transmission means and detected by mating reception means arranged in correspondence with a point of the capillary container.
The reception means are connected to a processing unit suitable to transform the values detected into an expression of the sedimentation speed, or other parameters correlated thereto, expressed in a unit of measurement compatible with those normally used.
According to the main characteristic of the invention, the pump means are arranged to suddenly interrupt the flow of blood flowing through the capillary, so as to cause a strong deceleration (stopped-flow) and then an aggregation and sedimentation of the blood cells as the blood compacts.
This compaction causes a variation in the signal detected by the detection means with a consequent acquisition of the information used to determine the ESR.
When detection is finished the blood sample analyzed is discharged from the circuit and the capillary is ready to receive a new blood sample to analyze
Since there are no centrifugal means it is possible to limit the length of the circuit wherein the blood circulates, and also eliminate the discontinuity and joints which create anomalies in the flow and encourage the formation of clots and bubbles.
On the one hand this allows to reduce the bulk of the whole apparatus and on the other hand to limit the quantity of blood needed to clean the capillary and for the analysis.
The configuration of the apparatus described allows it to be greatly reduced in size, and to be integrated in an optimum manner with pre-existing blood cells counting devices; consequently, the sample can be supplied to the capillary already in a condition of optimum homogenization, without the measuring apparatus needing auxiliary instruments for this function.
Moreover, with this apparatus, which requires microvolumes of blood in the order of 1-50 xcexcl, the analysis can be done with optimum results even on samples from children or new-born infants, where very little blood is taken and very small instruments have to be used.
In the apparatus according to the invention, the capillary container, the means to take the blood sample and the optical detection sensor may constitute a transportable structure which is distinct and separate from the processing unit and any optional system to display the results, and can be connected thereto by means of transmission cables or even via radio.
In this way, we obtain a great deal of flexibility and versatility of use, since the sampling and analysis instrument may be small in size and thus can be used, for example, directly from the bed of a patient, or under difficult conditions.
It is also possible to use a plurality of such apparatuses in parallel, to do the same test on different blood samples at the same time, or to use the same apparatus in series with other devices suitable to do different types of blood tests on the same sample.
Due to the very limited time needed for the test, the apparatus can also be used in local ambulatories, wards, mobile blood units or, as already mentioned, integrated with apparatuses suitable for blood tests of another type.
The apparatus allows to analyze the blood continuously and directly, immediately after it has been taken pure from the patient; it does not need anti-coagulants since the blood can be analyzed before the clot has time to form.
The detection means acquire data continuously, which allows a better evaluation of the optical density of the blood sample, and therefore an extremely precise measurement of the ESR; it also allows to detect any possible anomalies in the blood flow, for example due to air bubbles or clots.
The continuous study of the flow can also be used to determine other parameters of the rheology of the blood, such as the density or viscosity.
In a preferential embodiment of the invention, the pump means are reversible and allow to invert the flow inside the circuit; this allows to re-homogenize the blood sample and to rapidly repeat measurements thereof.
The capillary is suitable to be associated with a thermostat to allow analysis to be made at a constant temperature which can be set in advance as desired.
It is thus possible to make the same blood sample transit through capillary containers set at different temperatures and arranged in series, evaluating the ESR values according to the variation in the testing temperature.
In this case, it is preferable that at least one of the capillaries is maintained at a temperature of around 37xc2x0 C., in order to prevent the precipitation of some components of the blood and to guarantee a reliable control.